Contamination of Urban Watersheds: the Case of Arroio Moinho, Porto Alegre, Rio Grande do Sul, Brazil

Bruna Bonfim Rodrigues,Manoela Brum Poitevin Portella,Ana Maria Pimentel Mizusaki,Anderson Ribeiro De Figueiredo,Rualdo Menegat,Teddi Ann Galligan

doi:10.11137/1982-3908_2021_44_36744

Bruna Bonfim Rodrigues, Manoela Brum Poitevin Portella + Show 4 more

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https://doi.org/10.11137/1982-3908_2021_44_36744

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Abstract

This article aims to analyze the contamination of water and bottom sediment at Arroio Moinho (Mill Stream), in Porto Alegre (Rio Grande do Sul, Brazil). From two sample collections, a series of diagnostic measurements were carried out, such as: a) physical-chemical and biological analysis of the water; b) water quality index (WQI); c) metal contamination, granulometric and mineralogical analyses of the bottom sediment; d) total organic carbon (TOC); e) categorization into water quality classes; f) contamination factor (CF) and geoaccumulation index (Igeo) geoindicators; g) analysis of per capita income and population density. The analytical results of the water at the two sample locations exceeded the limits established by Class 4 (restricted use). The WQI revealed the worst level (very bad in 2012 and bad in 2018) at all sampling points. The bottom sediment analysis showed that the spring has a low fine-grained fraction content (3%) and TOC levels between 8 and 17%. However, the sediments revealed high levels of metals such as Zn and Cu and low to moderate Pb levels. These results allowed the stream to be classified as Class 3 in terms of soil quality, requiring identification of the source of the pollution and ongoing inspection to monitor contamination.

Highlights

Urban growth is causing concomitant environmental degradation in ecological systems (Knoll, Lübken, U. & Schott 2017; Perini & Sabbion 2017; Postel & Richter 2003; Rodrigues 2015; Smol 2008)
The results show that the water at the four points sampled in both 2012 and 2018 exceeded the standards determined in Class 3 (Table 5), a class that allows water to be destined for human consumption once it has undergone advanced treatment and that would be safe for uses involving potential human body contact
The high organic load released by the local population into the Arroio Moinho is causing high levels of contamination in the study area, as demonstrated by the results of this investigation

Summary

Introduction

Urban growth is causing concomitant environmental degradation in ecological systems (Knoll, Lübken, U. & Schott 2017; Perini & Sabbion 2017; Postel & Richter 2003; Rodrigues 2015; Smol 2008). & Schott 2017; Perini & Sabbion 2017; Postel & Richter 2003; Rodrigues 2015; Smol 2008) This is an important topic since the United Nations (2019a, 2019b) and the Population Reference Bureau (2020) estimate that the world’s urban population, by 2050, would increase by 60%, growing from 4.2 billion (4.2 x 109) in 2019, to 6.6 billion (6.6 x 109) inhabitants concentrated in cities. It is estimated that in 30 years, the country’s total population would grow 11%, reaching 232.9 million inhabitants This population projection associated with the current economic model that transforms forests, mineral resource, ecosystems in commodities points to an evident ecological collapse (Population Reference Bureau 2020; United Nations 2019a)

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